Magnetic polyphosphazene@Au particles as substrates for multiple-detection of immunoproteins by surface-enhanced Raman spectroscopy

Au coated magnetic polyphosphazene (MPCTP) composite particles ( [email protected] ) were fabricated with sensitive SERS activity. The MPCTP particles were generated by coating polyphosphazene on Fe 3 O 4 nanoparticles through precipitation polycondensation of hexachlorocyclotriphosphazene and phloroglucinol . [email protected] composite particles were obtained by deposition of Au nanoparticles on MPCTP by the reduction of HAuCl 4 . The size and the thickness of the Au shell can be controlled by varying the amount of HAuCl 4 . The magnetic core endowed the composite particles with good magnetic responsiveness, which allowed the analyte to be enriched and separated from the complex matrix, and significantly simplifying the sample pretreatment procedure. The SERS activity of [email protected] composite particles were evaluated by DTNB as model Raman reporter, and the limits of detection (LOD) of DTNB was 10 -8 mol/L. A high efficient SERS immunoassay system based on the [email protected] substrates for the detection of immunoproteins was developed. Human IgG and rabbit IgG were quantitatively determinated simultaneously by this immunoassay system. The quantitative determination of the immunoglobulin G (IgG) was achieved and the LOD of human IgG, rabbit IgG and the mixture of human IgG and rabbit IgG were as low as 10 fg/mL, 100 pg/mL and 1 ng/mL, respectively. The results showed that the [email protected] composite particles have broad application prospects as high performance SERS active substrates for immunoprotein analysis.